We investigate the melt chain dynamics of ultrahigh molecular weight polyethylene (UHMWPE) and its composites with graphene oxide (GO) nanosheets by means of neutron spin echo spectroscopy. For the GO concentrations explored, we observe hindered chain dynamics with respect to the pure UHMWPE. We propose a model where a fraction of the polymer is immobilized on top and at the bottom of GO sheets. This model enables us to provide a microscopic measurement of the adsorbed and free polymer fractions, as well as the thickness of the adsorbed layer. Our experiments provide experimental nanoscopic evidence of GO hindering entanglement formation in a polymer melt, a phenomenon that had been observed at the macroscale before via rheological measurements.